1. Field of the Invention
This invention relates to electrophotographic photoconductors, and more particularly to electrophotographic photoconductor whose photoconductive layer comprises at least one tertiary amine compound having a condensed polycyclic hydrocarbon group, and to tertiary amine compounds having a polycyclic hydrocarbon group which can be used as photoconductive materials in the photoconductors.
2. Discussion of Background
Conventionally, inorganic materials such as selenium, cadmium sulfide and zinc oxide are used as photoconductive materials of an electrophotographic photoconductor in the electrophotographic process. The above-mentioned electrophotographic process is one of the image forming processes, through which the surface of the photoconductor is charged uniformly in the dark to a predetermined polarity, for instance, by corona charge. The uniformly charged photoconductor is exposed to a light image to selectively dissipate the electrical charge of the exposed areas, so that a latent electrostatic image is formed on the photoconductor. The thus formed latent electrostatic image is developed by a developer comprising a coloring agent such as a dye and a pigment, and a binder agent such as a polymeric material, to a visible image.
Fundamental characteristics required for the photoconductor in such an electrophotographic process are:
(1) chargeability to an appropriate potential in the dark, PA1 (2) minimum dissipation of electrical charge in the dark, and PA1 (3) rapid dissipation of electrical charge when exposed to the light.
However, while the above-mentioned inorganic materials have many advantages, they have several shortcomings form the viewpoint of practical use.
For instance, a selenium photoconductor, which is widely used at present, completely satisfies the above-mentioned requirements (1) to (3), but it has the short-comings that its manufacturing conditions are difficult to control, and accordingly its production cost is high. In addition, it is difficult to work it into the form of a belt due to its poor flexibility, and it is so vulnerable to heat and mechanical shocks that it must be handled with the utmost care.
A cadmium sulfide photoconductor and a zinc oxide photoconductor can be easily obtained by coating a dispersion of cadmium sulfide particles and zinc oxide particles in a binder resin on a support. However, they are poor in mechanical properties, such as surface smoothness, hardness, tensile strength and wear resistance. Therefore, they cannot be used in the repeated operation, as they are.
To solve the above-mentioned problems of the inorganic materials, various electrophotographic photoconductors employing organic materials are proposed recently and some are put to practical use. For example, there are known a photoconductor comprising poly-N-vinylcarbazole and 2,4,7-trinitrofluorene-9-on, as disclosed in U.S. Pat. No. 3,484,237; a photoconductor prepared by sensitizing poly-N-vinylcarbazole with a pigment of pyrylium salt, as disclosed in Japanese Patent Publication 48-25658; a photoconductor comprising as the main component an organic pigment, as disclosed in Japanese Laid-Open Patent Application 47-37543; a photoconductor comprising as the main component an eutectic crystal complex of a dye and a resin, as disclosed in Japanese Laid-Open Patent Application 47-10735; a photoconductor prepared by sensitizing a triphenylamine compound with a sensitizer pigment, as disclosed in U.S. Pat. No. 3,180,730; a photoconductor comprising an amine derivative as a charge transporting material as disclosed in Japanese Laid-Open Patent Application 57-195254, a photoconductor comprising poly-N-vinylcarbazole and an amine derivative as a charge transporting material, as disclosed in Japanese Laid-Open Patent Application 58-1155, and photoconductors comprising as a photoconductive material a polyfunctional tertiary amine compound, especially a benzidine compound, as disclosed in U.S. Pat. No. 3,265,496, Japanese Patent Publication 39-11546 and Japanese Laid-Open Patent Application 53-27033.
Although the above photoconductors have excellent characteristics, and can be put in practical use, they are still unsatisfactory as photoconductors for use in electrophotography.